On the Micro-Behavior of rolling element of linear motion bearing

直线运动轴承的滑动单元是由多个在导轨上运行的滚动体承载的。根据滚动体表面微凸体的变形特性和润滑剂的特性，当滚动体运动较小时，滚动体的滚动行为表现为非线性和粘弹性，为了研究滚动体的这种微观行为特征，对一个直径为4 mm的滚动体进行了微滚动运动的实验观察。为了保持接触条件恒定，平行运动机构使用2个50 μ m厚的不锈钢板构造。该机构在轧制方向上具有很高的刚度，而在法向上具有柔性。用应变片测量驱动力，用间隙传感器（10 V/25 μ m）测量位移（滚动运动），在无润滑条件下进行加载和卸载驱动力的循环实验。当行程为9 um时，力和位移特性之间观察到滞后。另一方面，当行程为1 μ m时，没有观察到滞后，并且行为就像弹簧一样。法向力对其特性有影响。当法向力变大时，滞后变小。这可能是由于接触条件的改变，在有润滑剂的情况下，迟滞特性没有改变，但随着刚度的减小，力-位移特性发生了变化。从这些结果中发现，倾倒特性根据振动和法向力的振幅而非线性地变化。

The sliding unit of linear motion bearing is borne by many rolling element that run on the rail track. When the motion becomes rather small, its rolling behavior becomes non-linear and visco-elastic, according to the properties of deformation of asperities of the surface, lubricant and so on. This research aims to clarity such micro behavior characteristic of a rolling element.The micro rolling motion of one element(dia 4 mm) was experimentally observed. In order to keep the contact condition constant, the parallel motion mechanism was constructed using 2 stainless sheet metals of 50 um thickness. This mechanism s rigidity in rolling direction is very high, though flexible in the normal direction. The drive force was measured by strain gage, and the displacement(rolling motion) was measured by gap-sensor(10V/25 um).Cyclic experiment was performed with loading and unloading the driving force.under no lubricants. When the stroke was 9 um, hysteresis was observed between force and displacement characteristic. On the other hand, when the stroke was 1 um, no hysteresis was observed and the behavior was just like a spring. Normal force has a effect on its characteristic. When the normal force become large, the hysteresis becomes small. This may come from change in contact condition.Under the condition with lubricant, there is no change in hysteresis property, however, the force-displacement property has changed as to the rigidity becomes small.Free vibration experiment in normal direction were also performed. From these results, it was found that the dumping properties varies non-linearly according to the amplitude of vibration and normal force.